Electronic paper displays include an electronic paper display with a predetermined pattern. In such electronic paper display with predetermined pattern, an upper substrate includes a base substrate and a common electrode formed on the base substrate, and a lower substrate generally includes a base substrate and a pixel electrode with predetermined pattern formed on the base substrate. Display medium may be filled between the upper substrate and the lower substrate. The display medium may be electro chromism (EC) material or polymer dispersed liquid crystal (PDLC) material.
EC material may generate a reversible change between chromatic state of low transmittance and achromatic state of high transmittance by injecting or drawing charges (ions or electrons) under the effect of alternate high and low external field or alternate positive and negative external field. This is a special phenomenon that the physical performance of material is changed due to the electrochemical change, and exhibit a reversible change between specific color state and transparent state in terms of display state. Electro chromism material can achieve bi-stable state and requires a low driving voltage. A PDLC film can present two different optical states of transmission and dispersion under the effect of external field, such as, alternating current field, heat field, and so on. For example, the PDLC film presents dispersion state when electric field is not applied to the PDLC film, so that the region in the electronic paper display without electric field presents milk white. PDLC film presents transparent state when electric field is applied to the PDLC film, and the region in the electronic paper display applied with the electric filed presents transparent. Since the PDLC film does not need polarization sheet, rubbing alignment is not needed and large size flexible display is possible, thus the process is greatly simplified and the luminance and performance of the display is improved. Therefore, the above-mentioned EC material and PDLC film may be applied to electronic paper display, especially to such electronic paper display with predetermined pattern.
However, in the conventional electronic paper display, a pattern displayed in the pixel region has poor contrast with the non-pixel region, and color of the pattern is monotonic. For example, when the display medium is PDLC film, the pattern displayed in the pixel region is transparent, and the pattern in the non-pixel region is milk white. Furthermore, in the conventional electronic paper display, fringe field between the pixel electrode of the lower substrate and the common electrode of the upper substrate has prominent influence on the display medium and deteriorates the display quality.